Drying apparatus for granular material



Jan. 11, 1944. x G. B. TYLER 2,339,207

DRYING APPARATUS FOR GRANULAR MATERIAL Filed Feb. 16. 1945 s Sheets-Sheet 1 Inventor c: b. YLEQ By Attorney;

Jan. 11, 1944. G. B. TYLER ,2

DRYING APPARATUS FOR GRANULAR MATERIAL Filed Feb. 16, 1945 3 Sheets-Sheet 2 F/GTZ.

Inventor iORCE B.7'YLER- Attorney:

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I v u B TYLER Q DRYING APPARATUS FOR GRANULAR MATERIAL I I Filed Feb. 16, 1943 3 Sheets-Sheet 3 Inventor Gena: I3.TYL&1

Attorney;

Patented Jan. 11, 1944 OFFICE DRYING APPARATUS FOR GRANUL MATER IAL George Benjamin Tyler, London, England Application February 16, 1943, Serial No. 476,106 In Great Britain April 9, 1942 Claims.

This invention relates to rotary drying apparatus in which the material to be dried is brought into contact with heated air or other gases. The invention is particularly concerned with the collecting arrangements at the outlet end of the drying chamber. One form of apparatus to which the invention may be particularly well applied, consists of a drum which is slowly rotated about a horizontal axis or an axis which may be slightly inclined downwards towards the outlet end, and in which the material to be dried is supplied from a hopper at the inlet end, and as it travels towards the outlet end of the drum, is continually picked up by a, series of partitions or shelves from which the material cascades more or less in the form of a shower; heated air or other gas is introduced at the inlet end and continuously makes contact with the falling material.

In such apparatus, the dried material is collected in a casing at the outlet end, which often assumes the form of an enclosed hood, and is taken away or collected from a discharge outlet near the bottom of that casing, the heated air or gases and vapour being taken out separately. In drying materials in this way, it is known that the hot exit gases are liable to carry away with them a certain amount of the finelydivided material in the form of dust, and naturally it is desirable to recover this material from the current of gases. The usual practice is to take the gases off from-the upper part of the collecting casing and to pass them into a centrifugal separator of the cyclone class and the separated dust is added to the main bulk of dried material. Such an arrangement has certain drawbacks and inconveniences in operation. For example, some sort of conveyor, such as a screw conveyor, is provided for leading back the recovered fine material into the main bulk of the dried product. Also, since the hot gases are taken into a relatively cool cyclone casing, there is a liability for condensation of moisture to take place there, resulting in a certain amount of corrosion of the lower part of the separator casing which is often a conical casing leading to the discharge outlet at the bottom.

The object or the present invention is to device a convenient and compact form of apparatus in which these drawbacks no longer occur.

Thus, according to the invention, one or, more centrifugalseparators are built into the collecting casing or hood of the drying chamber in such a way that the gases in the collecting casing pass directly into the inlet of the separator or separators, no connecting pipe being needed in which the gases may be unnecessarily cooled, and the separator or separators being built into the casing are maintained at a relatively high temperature, so that condensation is avoided and any moisture present passes away into the outlet pipe with the hot gases which have been deprived of the finely-divided material.

Moreover, the collecting casing or hood is provided with a lower converging part with' a discharge outlet through which the main dried material from the drying chamber passes. The discharge outlets from the centrifugal separator or separators at their lower parts are arranged in the neighbourhood of the outlet from the main collecting casing or hood so that the separated finely-divided material is discharged directly into the main bulk of dried material within the collecting casing and no separate conveyor is required.

In order that the invention may be more clearly understood and readily carried into effect, two forms of rotary drum dryers with the delivery arrangements constructed in accordance with the present invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a side elevation, and

Figure 2 a plan of a rotary drum dryer with the improved delivery casing in which four cyclone separators are built in;

Figure 3 is a side elevation of the delivery end of a modified form of dryer; and

Figure 4 is an end elevation of Figure 3, the arrangement having two cyclones built into the collecting chamber; while I Figure 5 is a side elevation seen from the oppo.. site side to Figure 3,illust1ating an alternative form of deliverying valve from the cyclone separators.

Referring first of all to Figures 1 and 2, the drying drum A is mounted with its longitudinal axis slightly inclined and so as to be rotatable on two sets of rollers B on which tracks b secured to the drum A can roll. The drum is rotated by a ring of gear teeth 0 driven from a motor D through the worm gearing E and a spur pinion F. The drying drum A may be assumed to have a series of shelves which pick up the granular material and allow it to flow down in cascades and, for example, may be as gisclosed in British patent specification No. 461,-

At the inlet end, a stationary section G of the flue of a furnace H for supplying hot gases of combustion, spigots into the inlet end of the rotary drum A. The feed inlet for the granular material to be dried is fixed in the upper part of the section G and is shown at g. At the delivery end the drum A spigots-into a fixed section I attached to the collecting casing or hood K. This latter is a sheet metal casing of flat configuration and the lower part is furnished with a converging section L having a discharge outlet at Z for the dried granular material.

In this form of construction, four cyclone separators M are built into the collecting casing K.

They consist of cyclones with vertical axes with upper cylindrical parts m which lie towards and protrude from the top wall of the collecting casing K; they are provided with tangential inlets m opening towards the middle of the casing K so that the hot gases, on entering the casing K from the drying drum A, rise and pass directly into the tangential inlets m. The dust is separated in the ordinary way in the separators M and clean gases substantially free from dust pass out from the separators M into a clean gas trunk N. The separated dust subsides into the lower parts of the separators M which are of conical shape and are shown at 172 and each extends down just outside the cross-section of the drying drum A, ending in a tubular discharge m which is furnished with a discharge flap m shown more clearly in the embodiment illustrated in Figures 3 and 4. Each flap is pivoted and counter-balanced by a weight m which tends to close the flap m so that the latter is operated automatically by the weight of the dust when the latter accumulates in the outlet m to a predetermined extent. Access can be had to the flaps through inspection apertures k in the collecting casing K as shown in Figure 4, so that the flaps can be freed by hand if they are inclined to stick up. In this way, the dust drops out from the cyclones M and may be slightly directed by the convergent lower section L of the co1lecting casing K so that it rejoins the main mass of dried material and passes with it out through the discharge outlet Z without the need of a separate conveyor for the recovered dust.

The clean gas from the trunk N may be discharged to the atmosphere or partially re-circu-' lated into the furnace H at the inlet end of the drying drum A.

The modification shown in Figures 3 and 4 is arranged substantially similar to the form shown in Figures 1 and 2, and the same reference letters have been applied. In this case, however, only one pair of cyclone separators M is p vided, the separators being arranged side by side. IA fan is shown for extracting the clean warm gases from the trunk N and may pass from the fan delivery P to atmosphere or partially back to the furnace H, as shown in Figure 1. In Figures 3 and 4, a worm conveyor Q is shown for conducting the dried granular material away from the convergent section- L of the collecting casing K.

In Figure a further slight modification is shown, the main parts being as in Figures 3 and- 4, and the same reference numerals being em ployed. The only difference is that insteadfiof the flap valve m for each cyclone M, a rotary air-lock R is illustrated diagrammatically as an alternative air seal arrangement for each cy-- clone M.

Itwill be realised that in the two embodiments, the two or four cyclone separators being built into the collecting easing K are kept relatively warm" by the hot gases, with the result that no' condensation of moisture takes place in the separators M and any moisture in the gases passes away with the latter into the discharge manifold or trunk N. Moreover, the necessity for any separate conveyor for returning the separated dust from the lower ends of the cyclone separators M into the main bulk of the dried material in the section L of the casing K, is avoided whilst a more even distribution of the collected fine material from the separators M throughout the bulk of the dried material is obtained.

I claim:

1. Apparatus for drying granular materials comprising in combination, a rotary drying chamber furnished with inlets and outlets for the granular material and for heated gas, means for conveying the granular material from said granular material inlet to said granular material outlet, means for introducing heated gas into contact with the granular material within said drying chamber, an enclosed housing in communication with said drying chamber to receive therefrom the dried granular material and the heated gas and a centrifugal dust separator built into said housing and having its inlet open to the interior of said housing to receive the heated gas directly therefrom and having a discharge outlet for the separated dust delivering into the interior of said housing.

2. Apparatus for drying granular materials comprising in combination, a drying drum mounted to rotate about an inclined longitudinal axis and furnished with inlets for the granular material and for heated gas adjacent to its highor end and an outlet for the dried granular material and for exhaust gas at its lower end, an enclosed stationary housing connected to the lower end of said drying drum to receive therefrom the dried granular material and the exhaust gas and a centrifugal dust separator built into said housing and having its inlet open to the interior of said housing to receive the exhaust gas directly therefrom and having a discharge outlet for separated dust delivering into said housing.

3. Apparatus for drying granular materials comprising in combination, a drying drum mounted to rotate about an inclined longitudinal axis and furnished with inlets for the granular material and for heated gas adjacent its higher end and an outlet for the dried granular material and for exhaust gas at its lower end, an enclosed stationary sheet-metal housing connected to the lower end of said drying drum to receive therefrom the dried granular material and the exhaust gas, said housing having a lower converging section to form a discharge outlet for the dried granular material, and a centrifugal dust separator built into said housing and having its inlet open to the interior of said housing to receive the exhaust gas directly there from and having a discharge outlet for separat ed dust delivering into the main bulk of dried granular material in said lower con-verging sec: tio'ri of said housing.-

" 4.- A paratus for drying granular material's comprising in combination, a drying drum mounted to rotate" about an inclined longitudinal axis and furnished with inlets for the granular material and for heated gas adjacent its higher end and an outlet for the'dried granular materialand for exhaust gas at its lower end,- an en'- closed stationary housing" of flat configuration with a fiat upper'wall connected to lower end of said drying drum to receive therefrom the dried granular material and the exhaust gas and a pair of centrifugal dust separators supported side-by-side in. said upper wall of said housing and having their inlets open to the interior of said housing to receive the exhaust gas directly therefrom, their clean gas outlets delivering outside said housing and their discharge outlets for the separated dust delivering into the interior of said housing.

5. Apparatus for drying granular materials comprising in combination, a drying drum mounted to rotate about an inclined longitudinal axis and furnished with inlets for the granular material and for heated gas adjacent its higher 15 end and an outlet for the dried granular material and for exhaust gas at its lower end, an enclosed stationary housing connected to the outlet of said drying drum to receive therefrom the dried granular material and the exhaust gas and a plurality of cyclone dust separators built into said housing, each of said separators comprising a cylindrical upper section and a conical lower section with a tangential heated gas inlet open directly to the interior of said housing, a dust discharge outlet opening into the lower part of said housing and a clean gas outlet leading to the outer space above said housing.

GEORGE BENJAMIN TYLER.

- CERTIFICATE OF CORRECTION. Patent No. 2,559,207. January 11', 19141;. GEORGE BENJAMI N TYIER.

It is hereby certified that error appears in the printed specification .of the above numbered .patent requiring correction as follows: Page 1, first column, line L .8-b.9, for levice" read "devise"; page 4 2, first column, line 59, after "H, strike out as--; and that the said Letters Patent should be read with this correction I therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of February, A. D. 19%.

Leslie Fr'a'zer (Seal) Acting Commissioner of Patents. 

